1. Field of the Invention
The present invention is directed to managing low power modes in Integrated Circuits (ICs), and more particularly to providing a self-contained power management unit having intelligence and programmability separate from the main data processor for mobile multimedia devices.
2. Background Art
As more and more computing and multimedia facilities become available on mobile devices, there is an increasing need for a longer continuous operation of these devices without frequent charging of the battery. Another motivation for conserving the battery power is the increase of mobile applications, especially for business purposes where the devices in use are either away from a battery recharge source or there isn't enough time to recharge frequently. As a result, power consumption issues may limit the usability and performance of such mobile devices. Design techniques aimed at improving performance may therefore fall short if power management is not considered. To the same goal, power management units have been designed which operate at the low voltage ranges needed for these mobile devices to operate.
Present day devices have more and more features concomitant with the applications they are designed for. For example, the simple feature of alerting the user of an incoming call in a cell phone device can be performed in many ways, like electro-mechanical vibration of the device, emission of sound waves (phone-ring) or emission of light-waves. Each of these exemplary operations requires a varying amount of power. Using the same power level for such multiple features makes the functionality of the power management unit very inflexible.
An Integrated circuit device may be put into a ‘hibernate’ condition, where its voltage is so low that it can only save the state of its storage element, like volatile memory or shift registers. However, it cannot operate or function as far as running high level operations, multimedia applications, high speed data transfer or any CPU intensive processes are concerned. These devices may also be put into a very low voltage to a no voltage condition, wherein the capability to perform any external user related operations is not existent.
It is desired that in the above stated conditions, such devices should be capable of controlling the voltage source level, so that when needed, the voltage level can be increased to a level to allow higher level operations and functions and the transitions between different voltage levels be made possible.
Conventional power management devices do not have the capability to control their voltage source when in the zero to low power modes. They also lack any programmability for the same. There is also a lack of secure programmable power modes. There is thus, a need for a power management scheme flexible enough to accommodate varying power modes of an IC device and thereby provide the facility of managing and controlling the voltage source, independent of the main CPU or the processor, when the device is in one of such low power modes.